Alarm tag

ABSTRACT

An alarm tag made of two parts, one of which is provided with a pin (13) attached to the one part (12) to be located on one side of the product (11) with the pin extending through the product into locking engagement with the other part (10) located on the opposite side of the product. A resonance chamber (29), mounted in the one part (12), having a central outlet (30) is provided for activating the alarm device. A cover (19) is mounted on the one part (12) over the resonance chamber, and includes a central portion in register with the outlet (30), and bars (36) extending radially from the central portion (35) to the periphery of the cover, the bars defining slots (37) between adjacent bars.

FIELD OF THE INVENTION

The invention relates to an alarm tag comprising two parts one of whichis provided with a pin attached to said one part to be located on oneside of a product with the pin extending through the product intolocking engagement with the other part located on the opposite side ofthe product, said one part having means for activating an alarm devicein said one part.

BACKGROUND OF THE INVENTION

The alarm tag is of the type disclosed in PCT/SE95/00385 the content ofwhich is incorporated herein by reference.

The purpose of the invention is to further improve the security againstunauthorized removal of an alarm tag of the type referred to above fromthe product to be protected against theft by means of the alarm tag, andparticularly to minimize the possibility of attenuating the soundemitted from the alarm tag when the alarm is trigged due to manipulationof the tag.

GB-A-2 272 987 describes a gas driven alarm carried at the top end of aclosed tubular housing enclosing a liquid propellant container. Thecasing has an apertured frustoconical top portion the apertures in whichare located laterally in the top portion and are protected by flangesand finer inner mesh each aperture being located between adjacentflanges. The alarm device is essentially a conical volume with avibratory diaphragm at the narrow end and its larger mouth opening tothe outside radially of the frustoconical top portion through theapertures therein.

SUMMARY OF THE INVENTION

The present invention is an alarm tag comprising two parts, one of whichis provided with a pin attached to said one part to be located on oneside of the product with the pin extending through the product intolocking engagement with the other part located on the opposite side ofthe product, said one part having means for activating an alarm devicein said one part, characterized in that the alarm device comprises aresonance chamber having a central outlet, and a cover mounted on saidone part over said resonance chamber. The cover has a central portion inregister with the outlet and bars extending radially from the centralportion to the periphery of the cover. The bars define slots betweenadjacent bars. Other embodiments of the present invention are furtherdescribed hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to explain the invention in more detail reference is made tothe accompanying drawings which disclose an illustrative embodiment andwherein

FIG. 1 is a side view of an alarm tag attached to a product which isshown fragmentarily in cross section,

FIG. 2 is an enlarged side view of that part of the alarm tag whichcomprises a pin and a head,

FIG. 3 is a plan view of the pin part of FIG. 2,

FIG. 4 is a cross sectional view of the pin part of FIGS. 2 and 3 takenalong line IV--IV in FIG. 3,

FIG. 5 is a cross sectional view of a cover mounted on the pin part ofFIGS. 2 and 3, taken along line V--V in FIG. 3, and

FIG. 6 is a cross sectional view taken along line VI--VI in FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION

In FIG. 1 there is disclosed an alarm tag which comprises a first part10 containing means for initiating alarm from an alarm device whicheither is built into this part or consists of an external alarm device.The alarm is initiated when the alarm tag is carried out from a definedarea in a department store or a shop due to the fact that the alarm tagthen, at the exit from said area, will leave an electromagnetic orelectrostatic field maintained in said area, or is carried through sucha field maintained between bows located one at each side of the exitpassage. This part of the alarm tag can be of any existing knownconstruction. Part 10 is applied to one side of a product 11. The alarmtag also comprises a second part 12 consisting of a pin 13 with a head14 said head being applied to the opposite side of product 11 with thepin extending through the product and being attached to part 10. Theattachment is such that the parts cannot be moved apart for removal ofthe alarm tag from the product unless the attachment is operatedmagnetically or mechanically in a special device at the site where theproduct is to be paid, according to a well-known technique applied inconnection with alarm tags.

Part 12 is shown in detail in FIG. 4 and as can be seen head 14comprises a bottom plate 15 which has for example circular shape. Saidplate preferably is made of plastics of such kind that the plate isimpact resistant and elastically deformable and also can be fused. Asuitable material is for example polycarbonate. The plate has adownwardly extending peripheral rim 16 which stiffens the plate at theperiphery, and a central bulge 17 in which the pin is attached at a head18 formed on the pin. A cylindrical cover 19 which will be describedbelow in more detail is fused to plate 15 at 20. A circuit board 21carrying an electronic alarm circuit is located on top of plate 15. Anannular battery holder 22 and an inverted tray 23 on top of the batteryholder are clamped between circuit board 21 and cover 19, so thatdetails 21, 22 and 23 are firmly mounted between plate 15 and cover 19inside the cover. Two alkaline batteries 24 of the button type aremounted by means of battery holder 22 on circuit board 21 in electriccontact with the electronic alarm circuit on said board and areinterconnected in series by means of a contact blade spring 25 which iskept in contact with the batteries by means of the battery holder. Amembrane 26 comprising a piezo-electric ceramic element is attached tothe inverted tray 23 at the rim thereof and is connected with theelectronic alarm circuit on the circuit board 21 by means of helicalcontact springs 27 and 28. Membrane 26 defines together with tray 23 aresonance chamber 29 which communicates with the interior of cover 19through a central aperture 30 in tray 23. Normally, the electronic alarmcircuit is not energized. In order to energize the electronic alarmcircuit contacts 31 and 32 on the lower side of the circuit board 21must be interconnected.

A contact element for interconnecting contacts 31 and 32 comprises abistable spring washer 33 of metal located in a space defined betweencircuit board 21 and plate 15, and is attached at a central openingtherein to bulge 17 by the edge portion around the opening beingreceived in a circular circumferential groove 34 in bulge 17. The springwasher normally is in one stable position shown by solid lines, in whichthe spring washer is arched downwards and engages at the peripherythereof the upper surface of plate 15. When the spring washer is in thisposition the electronic circuit is de-energized and the alarm deviceaccordingly is passive. At any attempt to move the two parts of thealarm tag apart or to cut off the pin by means of a cutter or the likewhich is inserted between the parts pin 13 will be exposed to axialtension or be tilted, which causes deformation of plate 15. Due to suchdeformation of plate 15 the spring washer will snap to the other stableposition thereof which is shown by dot and dash lines in FIG. 4. In thisposition the spring washer is arched upwards in order to engage at theperiphery thereof contacts 31 and 32 at the lower side of the circuitboard 21 so that the electronic alarm circuit will be energized. Then,membrane 26 will be induced to oscillate at a predetermined frequencywhich is also the resonance frequency of resonance chamber 29, and soundwill be emitted through aperture 30. Preferably the sound is emittedintermittently at a predetermined repetition rate as a train of shortsound pulses. In order that the generated sound will be "let out" to thesurroundings through cover 19 this cover is of a specific design inorder to eliminate any possibility of non-scrupulous individualsmanipulating the device in order to suppress the sound so that it maynot be heard by people in the surroundings.

Cover 19 is constructed as a cage having a central portion 35 which isin register with aperture 30 in tray 23. The top wall of the cover isslightly arched and comprises uniformly distributed bars 36 whichproject from central portion 35 to the periphery of the cover the widthof said bars increasing from portion 35 towards the periphery of thecover so that adjacent bars define a radial slot 37 of uniform width. Atthe periphery of the cover the bars extend axially downwards. The axialportion of each bar has uniform width. Bars 36 are channelled at theback side thereof not only in the axial portion as will be seen in FIG.6, but also in the top wall portion, and have a web 38 and side flanges39. The spacing between adjacent axial portions of bars 36 is covered bya web 40 the lower end of which is spaced from the lower edge of cover19 formed by bars 36, rim 16 of wall 15 being received inside the coverbelow webs 40 to be fused to said webs at 20. The lower ends of theaxial portions of bars 36 terminate a small distance from the lower edgeof rim 16 at 41.

A space 42 is defined between tray 23 and cover 19 at the top wallthereof said space communicating with resonance chamber 29 throughaperture 30. Normally the sound produced by membrane 26 in resonancechamber 29 when the electronic alarm circuit is energized will betransmitted to space 42 and from there to the surroundings through slots37. Now, if these slots are covered by the hand or by means of a plasticmass such as chewing gum in an effort to suppress the sound in case thealarm tag is being manipulated the sound will still pass through thechannels formed by bars 36 so that the sound will be transmitted to thesurroundings at 41 where said channels open spaced from product 11.These openings cannot easily be covered.

In the premises where the alarm tag is being used there can be provideda receiver which is tuned to the frequency and repetition rate of thesound transmitted by the alarm tag when energized even if such sound isattenuated by manipulation of the alarm tag, and which is trigged by thesound in order to energize one or more alarm devices provided in thepremises, so that this alarm device or these alarm devices emit a strongalarm sound in the premises if the alarm tag is being manipulated.

If the alarm device has been activated it can be shut off by the springwasher being brought to snap back to the position shown by solid lines,but such resetting should of course be possible only in a deviceprovided especially for that purpose by actuation of the spring washer.

I claim:
 1. Alarm tag comprising two parts one of which is provided witha pin (13) attached to said one part (12) to be located on one side of aproduct (11) with the pin extending through the product into lockingengagement with the other part (10) located on the opposite side of theproduct, said one part having means for activating an alarm device insaid one part, characterized in that the alarm device comprises aresonance chamber (29) having a central outlet (30), and a cover (19)mounted on said one part (12) over said resonance chamber, said coverhaving a central portion in register with said outlet (30), and bars(36) extending radially from said central portion (35) to the peripheryof the cover, said bars defining slots (37) between adjacent bars. 2.Alarm tag as in claim 1, characterized in that said bars (36) extendalong a side wall of the cover.
 3. Alarm tag as in claim 1 or 2,characterized in that said bars (36) are channelled at the back sidethereof.
 4. Alarm tag as in claim 3, characterized in that the channelsformed by said bars (36) open at the lower end thereof spaced from thelower side of said one part (12).